1. Field of the Invention
The present invention relates to an image pickup system including a camera platform apparatus, and specifically relates to an image pickup system having a function that stores panning/tilting positions of a camera platform apparatus and drives the camera platform apparatus to the stored panning/tilting positions.
2. Description of the Related Art
Conventionally, camera platform apparatuses that pan/tilt using remote control from a remote operation apparatus in image pickup systems including an autofocusing unit have been known.
For autofocusing when a camera platform apparatus is used, an arbitrary area of an image pickup screen is made to a region subject to autofocusing, and an image pickup lens for focusing is driven according to a distance to an object in the region. Then, upon the camera platform apparatus being panned/tilted, the object on camera is changed from one to another and the focus state changes, and thus, the autofocusing unit sets a focus value again.
Autofocusing here means contrast AF or phase-difference AF. Contrast AF is a method in which focusing is performed by controlling an image pickup optical system based on the magnitude of a high-frequency component of an output signal obtained from an image sensor. Phase-difference AF is a method in which a distance to an object is measured using the principle of triangulation using two sensors.
Also, remote operation apparatuses have a preset function. The preset function registers, e.g., panning/tilting target positions desired by an operator and a target position for a focus value in a storage unit as a preset position. Then, the operator gives an instruction to reproduce the preset position, driving is performed so that the panning/tilting positions and the focus value reach the respective target positions. Hereinafter, an operation in which an instruction to reproduce a preset position is input, driving is performed so as to drive to the target positions and the target positions are reached is referred to as a shot operation.
For example, Japanese Patent Application Laid-Open No. H09-205573 describes a method for controlling autofocusing when a camera platform apparatus including a camera lens is subject to the pan/tilt operation.
In Japanese Patent Application Laid-Open No. H09-205573, immediately after provision of an instruction to reproduce a preset position using a preset function of a remote operation apparatus, a focus lens unit is instantly driven to a target position and panning/tilting operation is performed to the panning/tiling target positions. Then, upon the target positions being reached, an autofocusing function is activated to perform focusing on a true image pickup position.
During panning/tilting, the object is sequentially changed from one to another, resulting in instability of a focal position of a focus lens unit. Therefore, in the above technique, autofocus operation is not performed during panning/tilting rotation and the focus lens unit is instantly driven to a target position so as to prevent the focusing operation during panning/titling from becoming unstable. Also, the autofocusing function is activated after reaching the target positions to prevent from providing an out-of-focus image because an object registered via the preset function and an object after a shot operation may be different from each other.
However, the aforementioned conventional technique disclosed in Japanese Patent Application Laid-Open No. H09-205573 has the following problems. First, in a shot function in which the panning/tilting positions and the conditions such as focusing and zooming of an optical system are forcibly driven to preset conditions, if an object distance registered via a preset function and an object distance after the shot operation are different from each other, an out-of-focus image of the object is obtained until the camera returns to an autofocusing state and performs focusing using autofocusing after the shot operation. Also, during panning/tilting operation to the target panning/tilting positions using a shot function, autofocusing does not work, and thus, an image picked up during the rotation is highly likely blurred. As described above, it is highly likely that an image is blurred after and during a shot operation, resulting in the image providing a feeling of strangeness.